Handbook WG - Create a new network chapter

Create a new chaper with the basic configuration of a wired
and wireless networks in FreeBSD.

Sections of the new chapter:

• Synopsis
• Setting up the Network
• Wired Networks
• Wireless Networks
• Hostname
• DNS
• Troubleshooting

Changes:

• Move wired network section from config to network
• Move virtual hosts section from config to advanced networking
• Move basic wireless section from advanced networking to network
• Move IPv6 from advanced networking to network
• Upgrade all command outputs
• Use sysrc
• Improve AsciiDoc syntax

Differential Revision: https://reviews.freebsd.org/D40546
Reviewed by: bcr, dbaio, fernape, karels
Sponsored by: Daifressh